In general, there are known turbine rotor blades having shrouds (tip shrouds) at the blade ends thereof, which are used for a gas turbine or the like. When a vibration occurs in the turbine rotor blades, the shrouds of adjacent turbine rotor blades abut against each other, thereby suppressing the vibration.
The above-described shrouds of the turbine rotor blades have been reduced in weight in terms of strength.
In particular, while turbine rotor blades have been increased in length and height due to a recent increase in turbine capacity caused by an increase in turbine output, the shrouds of turbine rotor blades that are disposed at the downstream side of a gas flow in the gas turbine, for example, turbine rotor blades that are disposed at a third stage or a fourth stage in the turbine, have been reduced in weight in order to reduce the centrifugal load as much as possible because, during rotation, a larger centrifugal load is imposed on those turbine rotor blades than on other turbine rotor blades that are disposed at the upstream side.
Furthermore, it is difficult to ensure the strength of the turbine rotor blades because the temperature of working fluid flowing around the turbine rotor blades has been increased in order to increase the turbine output, and, therefore, a reduction in the weight of the shrouds is achieved in order to reduce the strength required for the turbine rotor blades as much as possible.
Specifically, a partial-cover shape for covering only part of the space between blade portions of the turbine rotor blades is adopted as the shape of each shroud, thereby achieving a reduction in the weight of the shroud (NPL 1).